Evaluating sulfur-impurity removal and modern carbon contamination in different preparation methods for radiocarbon dating of soil samples by accelerator mass spectrometry

Koarashi, Jun   ; Takeuchi, Erina; Kokubu, Yoko   ; Atarashi-Andoh, Mariko  

Radiocarbon (C) dating of soil samples by accelerator mass spectrometry has been proven useful for studying carbon (C) cycling in terrestrial ecosystems. There are, however, two main difficulties in sample preparation for this application: contamination of samples with modern C and inhibition of graphite formation due to sulfur (S)-containing impurities. Here we evaluated these effects from three different sample preparation methods, by conducting C measurements of C-dead sample and S-rich soil samples. The preparation methods were all successful in graphite formation and C measurement for soil samples with an organic S content 6.9%. The different methods showed different percent Modern Carbon (pMC) values ranging from 0.19% to 0.64% for C-dead sample. However, the three methods had little influence on the determination of C age for samples at least younger than 12,000 yr BP. The methods examined in the present study can be used for C dating with sufficient accuracy in the application to C cycle studies.